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Commit ea309944 authored by Ulf Hansson's avatar Ulf Hansson Committed by Rafael J. Wysocki
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PM / Runtime: Update documentation around probe|remove|suspend 



PM core and driver core has changed some behavior regarding use of
runtime PM. Update the documentation accordingly.

Signed-off-by: default avatarUlf Hansson <ulf.hansson@linaro.org>
Signed-off-by: default avatarRafael J. Wysocki <rafael.j.wysocki@intel.com>
parent baab52de

Documentation/power/runtime_pm.txt

+6 −8
Original line number Diff line number Diff line
@@ -547,13 +547,11 @@ helper functions described in Section 4. In that case, pm_runtime_resume() 
should be used.  Of course, for this purpose the device's runtime PM has to be

enabled earlier by calling pm_runtime_enable().



If the device bus type's or driver's ->probe() callback runs

pm_runtime_suspend() or pm_runtime_idle() or their asynchronous counterparts,

they will fail returning -EAGAIN, because the device's usage counter is

incremented by the driver core before executing ->probe().  Still, it may be

desirable to suspend the device as soon as ->probe() has finished, so the driver

core uses pm_runtime_put_sync() to invoke the subsystem-level idle callback for

the device at that time.

It may be desirable to suspend the device once ->probe() has finished.

Therefore the driver core uses the asyncronous pm_request_idle() to submit a

request to execute the subsystem-level idle callback for the device at that

time.  A driver that makes use of the runtime autosuspend feature, may want to

update the last busy mark before returning from ->probe().



Moreover, the driver core prevents runtime PM callbacks from racing with the bus

notifier callback in __device_release_driver(), which is necessary, because the
@@ -656,7 +654,7 @@ out the following operations: 
    __pm_runtime_disable() with 'false' as the second argument for every device

    right before executing the subsystem-level .suspend_late() callback for it.



  * During system resume it calls pm_runtime_enable() and pm_runtime_put_sync()

  * During system resume it calls pm_runtime_enable() and pm_runtime_put()

    for every device right after executing the subsystem-level .resume_early()

    callback and right after executing the subsystem-level .resume() callback

    for it, respectively.